Optimizing magnetocaloric and thermoelectric performance of MnCoGe/BiSbTe composites by regulating magnetostructural transition and element diffusion.

Composites consisted of MnCoGe magnetocaloric alloy and BiSbTe thermoelectric alloy were prepared to explore their potential use in all-solid-state cooling. It was found that in the composites the phase transition of MnCoGe from orthorhombic to hexagonal phase causes a large drop of magnetostructural transition temperature from room temperature to 270 K. The diffusion of Mn into BiSbTe leads to the formation of interfacial phase Mn(Bi,Sb) 2 Te 4 and doping effect that depresses the thermoelectric performance. By adopting a low-temperature sintering strategy, the phase transition was restricted and the doping effect due to Mn diffusion was alleviated. As a result, the magnetostructural transition temperature around 300 K is maintained and the room-temperature magnetocaloric and thermoelectric properties are simultaneously optimized. The maximum magnetic entropy change of 4.3 × 10−3 J kg−1 K−1 at 2.0 T and maximum ZT value of 0.81 at 384 K have been obtained on the composite incorporated with 1 wt % MnCoGe. This work demonstrates that the control of phase transition and the doping effect of MnCoGe is crucial in optimizing the thermo-electro-magnetic properties of MnCoGe/BiSbTe composites. • The diffusion of Mn and formation of interfacial phase Mn(Bi,Sb) 2 Te 4 in MnCoGe/BiSbTe thermo-electro-magnetic composites were identified by the atomic-resolution STEM, which is crucial in affecting the thermoelectric and magnetocaloric performance. By regulating the magnetostructural transition and element diffusion, enhanced thermoelectric and magnetocaloric properties were realized in the composites. [ABSTRACT FROM AUTHOR]